Registration Dossier

Environmental fate & pathways

Hydrolysis

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Administrative data

Link to relevant study record(s)

Description of key information

No data are put forward as this endpoint is not relevant for molybdenum, and metals in general 

Key value for chemical safety assessment

Additional information

Under REACH (ECHA 2008, Chapter R.7B – Endpoint Specific Guidance), the term ‘Hydrolysis’ refers to the “Decomposition or degradation of a chemical by reaction with water”, and this as a function of pH (i.e., abiotic degradation). The need for testing may be waived if “The substance is highly insoluble in water”, or if “The substance is readily biodegradable”. The latter property of a substance assumes a rapid mineralization of the substance and therefore hydrolysis tests will provide little information.

In the case of the current substance, the chemical safety assessment will be based on elemental metal concentration, i.e., the assessment of molybdenum is conducted regardless of the (pH-dependent) speciation in the environment. Hence, as the assessment is based on the element concentration (i.e.,Mo as molybdate), physicochemical processes like decomposition and degradation by reaction with water are not relevant. Formation of different Mo-forms may occur at specific pH-levels, but the chemical assessment will not make any differentiation among the differentMo-species (pooling of different speciation forms). This elemental-based assessment (pooling together of all speciation forms) can be considered as a worst-case assumption for the chemical assessment.

In general, (abiotic) degradation is an irrelevant process for inorganic substances that are assessed on an elemental basis.